杨树木质素组分的调控对于其生产应用具有重要意义，已证实F5H是调控木质素S/G比例的关键酶。因此解析F5H的调控机制对于林木育种十分重要。课题组前期在杨树中鉴定到木质素代谢相关酶PtrCSE1/2、PtrMYB10/128转录因子和miR6443小RNA影响F5H表达，但调控机制尚不清楚。为此本项目拟：检测PtrCSE1/2敲除杨树的代谢产物、基因表达和木质素组分，探索代谢流影响F5H表达和木质素组分机理；分析超表达和突变体杨树次生壁形态与组分，解析PtrMYB10/128的功能；转录组测序筛选PtrMYB10/128的靶基因，阐明F5H的转录调控网络；RACE和遗传分析解析miR6443对F5H的调控机制；在转基因杨树中探究miR6443对木质素组分的作用。最终阐明代谢流、转录因子和表观作用三个层次的F5H调控方式在杨树木质素单体合成中的协同机制，为杨树木质素组分改良育种奠定理论基础。

Lignin content and composition play pivotal roles in the properties and applications of wood. Ferulate 5-hydroxylase (F5H) has been proven a key enzyme in the regulation of S/G ratio in lignin, thus it is critical for the molecular breeding of trees for wood production to elucidate the regulatory mechanism of F5H. We have previously identified several factors that show influence on F5H expression in Populus, including PtrCSE1/2, the enzymes involved in lignin metabolism, PtrMYB10/128, MYB family transcription factors, and miR6443, a microRNA. However, it remains unclear how these various factors are involved in the regulation of F5H expression. Therefore, we plan to: 1) determine the metabolite composition, gene expression and lignin composition in PtrCSE1/2 knock-out poplar to clarify how F5H expression and lignin composition areinfluenced by metabolite cascade; 2) analyze the morphology and composition of thesecondary cell wall in PtrMYB10/128 over-expression and knock-out poplar to elucidate their biological functions; 3) screen target genes of PtrMYB10/128 by transcriptome sequencing and clarify the regulatory network for F5H transcription; 4) elucidate the regulatory mechanism of miR6443 against F5H by RACE and genetical analysis; 5) determine the influence of miR6443 on lignin composition in transgenic poplar. Finally, establish a coordinated regulatory mechanism on lignin monomer biosynthesis through metabolite cascade, transcription factor and epigenetic regulations on F5H expression in poplar, so as to set up theoretical foundations for the breeding of poplar with modified lignin composition.